Numerous hormonal methods for contraception are known, i.e., the oral administration of combination-type preparations, e.g. "Ovulen", "Anovlar", "Lyndiol", and similar combinations of estrogenic and gestagenic active agents. Also conventional is the administration of purely sequential preparations, such as, for example, "Ovanone", etc., wherein first an estrogen is administered at a high dosage in the absence of gestagen, over a period of 7 days, and thereafter the estrogene is administered at the same high dosage in combination with a relatively high amount of gestagen over a period of 15 days, with the next 6 days being a blank period without administration of estrogenic or gestagenic agent in order to mimic the normal 28-day menstrual cycle of the woman.
The administration of modified sequential preparations is likewise conventional, such as, for example, "Kombiquens", "Tri-Ervonum", and "Oraconal", etc., wherein first an estrogen is administered at a high dosage in combination with a low amount of gestagen over a period of 16 days, and subsequently the estrogen is administered over a period of about 7 days at the same high dosage in combination with an amount of gestagen about 5-10 times the original amount. See U.S. Pat. No. 3,568,828. To adapt to the natural 28-day cycle of the female, a 5-day hormone-free period follows the administration of these preparations wherein placebos or any desired other non-contraceptive effective agents are taken, such as, for example, tonics, iron supplements, etc.
The disadvantages of the administration of the above-mentioned sequential preparations are, in particular, the relatively high doses of estrogen, resulting, in addition to evoking the customary symptoms caused by an excess of estrogen, such as, for example, gastrointestinal disturbances, nausea, weight gain from edema, etc., along with an increase in the risk of thromboembolism. On the other hand, however, it was considered essential to ingest high doses of estrogen for reliable contraceptive effect.